Forum Discussion
SMTP server blacklisted?
As of about 7 p.m. EDT this evening (08/18/18), I am not able to send any emails, as I am getting the message that the HughesNet SMTP server IP address is blacklisted. Is this one of those things wh...
Turns out smtp.hughes.net [69.168.97.48] is listed on spam.dnsbl.sorbs.net (as is smtp.lithium.com [208.74.204.5], btw).
Not to be pedantic, but that shouldn't technically prevent you from sending email. Some email servers my reject receiving it, preventing the intended recipient from getting it.
How exactly are you getting notified of this? Bounce email from the receiving server, perhaps?
Edit:
Liz
Amanda
Note to admins. I did notice this in the headers. Probably want to have the tech folks fix the SPF in your DNS entry:
Received-SPF: neutral (smtp01.hughes.cmh.synacor.com: 97.73.80.47 is neither permitted nor denied by domain of hughes.net)
Setting the SPF helps to validate email from a specific domain and might alleviate getting listed on some blacklists due to forged/stolen senders coming from other email servers.
Edit2:
To do this, add a TXT record to the DNS entry that says something like:
v=spf1 a mx ip4:97.73.80.47 -all
The IP was taken from above, but it might have to be duplicated for the various servers used by Synacor (e.g., if there's a smtp02, smtp03, etc.).
Did manage to check the SPF record using a third party tester that I use for my own domain(s).
Seems the record is there (and includes quite a range of allowable IPs) but is terminated by a '?'. That's what's causing the neutral response. If the '?' is changed to a '-all' it will cause the forged emails to fail.
You can also add a TXT record to implement DMARC reporting of successful/failed emails based on SPF and DKIM (if that's also implemented - doesn't look like it though).
